Echoes of the forest: Assessing Reforestation in the Mata Atlântica through Soundscape Analysis

This research aims to assess the effectiveness of different management strategies and reforestation efforts in the conservation of the Brazilian Atlantic Forest using soundscapes as a primary data source. Fieldwork was conducted at the Iracambi Research Center, an NGO located in the state of Minas Gerais, Brazil, committed to the protection and reforestation of the Atlantic Forest, one of the most biodiverse and threatened biomes on the planet. Six forest management categories were studied: Primary Forest, Secondary Forest, Reforested Area, Montane Forest, Eucalyptus Plantation, and Pasture. Soundscape recording devices were deployed in three plots per category, capturing data for one minute every five during the dry season. The recordings were analysed using acoustic indices—mathematical metrics that act as biodiversity indicators—calculated for four time periods: dawn, midday, dusk, and midnight. The primary hypothesis of this study was that pristine areas would exhibit more complex soundscapes compared to disturbed ones and that reforested areas would present an acoustic diversity comparable to secondary forests. Additionally, it was hypothesized that acoustic diversity would correlate positively with arboreal diversity, evenness and biomass, underscoring the role of vegetation structure in shaping acoustic communities. It was also expected a relationship between acoustic indices and meso-mammal species richness in the plots. The findings showed that reforested areas can reach levels of acoustic diversity similar to those of secondary forests, suggesting their ecological value in restoring biodiversity within shorter timeframes. Pastures presented unexpectedly high acoustic diversity, likely driven by invertebrate activity, while eucalyptus plantations were characterized by low acoustic diversity. Acoustic indices, particularly the Acoustic Diversity Index (ADI) and the Acoustic Evenness Index (AEI), were significantly correlated with tree diversity and evenness, but not with biomass, suggesting that tree diversity is a stronger determinant of soundscape complexity than tree volume. Meso-mammal species richness also showed weak correlation with acoustic diversity in all the time spans considered. This study highlights the potential of soundscape analysis as a powerful tool for monitoring biodiversity in differently managed forests, offering insights into conservation strategies in tropical ecosystems.